1. Field of the Invention
The present invention relates to an image pickup unit, and more particularly to an image pickup unit which is arranged in a distal end portion of an endoscope and which includes an optical reflection member for refracting and reflecting photographing light.
2. Description of the Related Art
In recent years, endoscopes have been widely used in medical fields and industrial fields. The endoscopes include a conventional fiberscope type endoscope for observing an observation image through an eyepiece by using an image fiber, and an electronic endoscope in which a solid-state image pickup device is arranged in an endoscope distal end portion, an endoscope operation portion, or the like, and which displays an observed image in a monitor.
The conventional electronic endoscope includes, as disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 61-254917 and Japanese Patent Application Laid-Open Publication No. 4-317622, a type using a configuration in which, in order to achieve slenderization by effectively using a space in a distal end portion, photographing light is refracted and reflected by a prism in the direction approximately perpendicular to the longitudinal axis of the distal end portion, and in which a light receiving surface of a solid-state image pickup device forming an image of the photographing light, is arranged at a position so as to be in parallel with the longitudinal axis of the distal end portion.
In the conventional image pickup unit, there is arranged a prism holding base, or a reinforcing member brought into contact with or fixed to an inclined surface on which the reflection surfaces of two prisms are formed. The conventional image pickup unit is arranged and fixed in the distal end portion of the endoscope in such a way that the reinforcing member or the prism holding base is fixed to the distal end portion of the endoscope with screws.